| Sencare Limited | Health & social care | 2019 |
| Sendeliv Ltd | Transport & logistics | 2025 |
| Sendsendsend Limited | Health & social care | 2024 |
| Seneca Projects Ltd | Information & communication | 2018 |
| Senflow Limited | Information & communication | 2025 |
| Senior Engineering Services Limited | Wholesale & retail | 2002 |
| Senior Legal Recruiter Limited | Professional & scientific | 2017 |
| Senior Product Development Limited | Professional & scientific | 2018 |
| Senior Stairlifts Ltd | Wholesale & retail | 2019 |
| Senior Support Ltd | Administrative & support | 2021 |
| Senna Properties Ltd | Real estate | 2024 |
| Sennar Bodyworks Limited | Wholesale & retail | 2025 |
| Seno Technologies Limited | Information & communication | 2019 |
| Sensation Express Couriers Ltd | Transport & logistics | 2026 |
| Sense of Occasion Ltd | Wholesale & retail | 2020 |
| Sense of Space Interiors Ltd | Professional & scientific | 2023 |
| Sense-A-Reaction Limited | Education | 2020 |
| Sensecare Franchising Limited | Health & social care | 2016 |
| Sensecare Limited | Health & social care | 2013 |
| Senseless Ltd | Wholesale & retail | 2026 |
| Sensen Ltd | Other services | 2025 |
| Senses Learning Hub Ltd | Education | 2024 |
| Sensia Torsion Care Homes Limited | Construction | 2026 |
| Sensia Torsion Devco Limited | Construction | 2026 |
| Sensible Financial Planning Limited | Financial services | 2024 |
| Sensory Scope CIC | Education | 2025 |
| Sentao Services Ltd | Professional & scientific | 2009 |
| Sentenced Limited | Wholesale & retail | 2019 |
| Sentient Group Limited | Administrative & support | 2022 |
| Sentinam Liquid Movement Solutions Limited | Administrative & support | 2024 |
| Sentinel Capital Holdings Ltd | Other services | 2018 |
| Sentinel Force Security Limited | Administrative & support | 2023 |
| Sentinel Ironcraft Company Limited | Manufacturing | 2017 |
| Sentinelrx Life Sciences and Technologies Ltd | Information & communication | 2024 |
| Sentinels Property Ltd | Real estate | 2024 |
| Sentinent Ventures Ltd | Wholesale & retail | 2026 |
| Sentio Partners LLP | | 2012 |
| Sentop Solution Limited | Information & communication | 2025 |
| Sentry Associates Limited | Professional & scientific | 2007 |
| Sentry Secure Intelligence System Limited | Information & communication | 2013 |
| Sentyfi Limited | Administrative & support | 2025 |
| Seoteric Ltd | Professional & scientific | 2024 |
| SEP2 Limited | Information & communication | 2016 |
| Sepher Limited | Financial services | 2023 |
| Sephton Transport Limited | Transport & logistics | 2000 |
| SEPTEMBER08 Limited | Financial services | 2016 |
| Sera Yorkshire Ltd | Financial services | 2015 |
| Seraphina Corporation Ltd | Wholesale & retail | 2024 |
| Seratoner Celebrations Ltd | Other services | 2025 |
| Seratoner Events Ltd | Administrative & support | 2025 |
| Serda Ltd | Administrative & support | 2013 |
| Serendipity Aesthetics Ltd | Other services | 2025 |
| Serene Oasis Ltd | Construction | 2024 |
| Serene Perfection Ltd | Information & communication | 2024 |
| Serene Starts Ltd | Health & social care | 2025 |
| Serenekey Limited | Real estate | 2025 |
| Serenity Doors & Windows Ltd | Wholesale & retail | 2026 |
| Serento Ltd | Health & social care | 2024 |
| Sergeant Principal Ltd | Real estate | 2022 |
| Sergent Courier Ltd | Transport & logistics | 2025 |
| Sergiu Consult Ltd | Transport & logistics | 2025 |
| Sergiu Petrica Ltd | Transport & logistics | 2022 |
| Serif Systems Limited | Information & communication | 1994 |
| Seriously RAD Limited | Information & communication | 2016 |
| Serrabros Ltd | Transport & logistics | 2026 |
| Serrano Investments Ltd | Real estate | 2021 |
| Serrano Stays Ltd | Real estate | 2019 |
| Serrano Yorkshire Ltd | Financial services | 2025 |
| Serval Consulting Limited | Information & communication | 2015 |
| Servatech (Holdings) Limited | Professional & scientific | 2009 |
| Servecool Limited | Information & communication | 2002 |
| Servemet (N.W.) Limited | Wholesale & retail | 1981 |
| Serventi Group Ltd | Construction | 2026 |
| Server Parts Limited | Wholesale & retail | 2003 |
| Serverless Studio Limited | Information & communication | 2025 |
| Serverteam Limited | Information & communication | 2007 |
| Servia Digital Ltd | Information & communication | 2025 |
| Service Integration Ltd | Information & communication | 2014 |
| Service Transition Consultants Ltd | Information & communication | 2023 |
| SERVICE2U (UK) Limited | Other services | 2014 |
| Serviced Apartment Real Estate (Kingston Centro) Limited | Real estate | 2024 |
| Serviced Apartment Real Estates (Walton Centro) Limited | Real estate | 2024 |
| Serviced Media Limited | Professional & scientific | 2025 |
| Services 24/7 Limited | Administrative & support | 2025 |
| Services Assistant Limited | Administrative & support | 2020 |
| Services Support (Avon & Somerset) Holdings Limited | Professional & scientific | 2003 |
| Services Support (Avon & Somerset) Limited | Construction | 2003 |
| Services Support (SEL) Holdings Limited | Professional & scientific | 2000 |
| Services Support (SEL) Limited | Administrative & support | 1998 |
| Servizi Limited | Other services | 2016 |
| Servo Securities Limited | Administrative & support | 2013 |
| Servo Security Services Ltd | Administrative & support | 2024 |
| Sesame Fine Food Ltd | Hospitality | 2022 |
| Sesame Healthy Food Limited | Hospitality | 2016 |
| SET Visions Limited | Professional & scientific | 2008 |
| Setech Security Limited | Administrative & support | 2016 |
| Seth & Sons Lucianos Ltd | Hospitality | 2026 |
| Seth Mater Ltd | Wholesale & retail | 2024 |
| Seth's Healthcare Limited | Wholesale & retail | 2019 |
| Setna Limited | Wholesale & retail | 2023 |